1. Technical Field
The present invention relates in general to manufacturing magnetic media and, in particular, to an improved system, method and apparatus for manufacturing magnetic recording media.
2. Description of the Related Art
Patterned magnetic recording disk substrates have patterns that are typically formed with nano-imprint lithography processes. As shown in FIG. 1, a rigid mold 11 is provided with at least the same diameter as the disk to be patterned and is formed from a hard material, such as quartz. Curable resist 13 is applied to the rigid disk or substrate 15 to be patterned, and the rigid mold 11 is pressed onto the resist.
Under pressure, the resist flows to uniformly coat the non-patterned interstices on the disk with a uniform thickness, while also filling the recesses in the rigid mold. Radiation (e.g., UV light or heat) is applied through the quartz to cure the resist. The rigid mold is then separated from the cured resist and the disk, now coated with the patterned resist, is subsequently processed through etching and cleaning.
One problem with this technique is that when two rigid surfaces are brought together within several hundred nanometers of each other, any foreign hard particles 17 that are present between the surfaces affect the pattern formed. This is particularly true for particles having dimensions larger than the gap between the surfaces. This effect may be advantageously utilized for some applications, such as with flat panel displays in the manufacturing of thin-film transistor liquid crystal displays. Spacer particles with precise dimensions are employed to maintain a uniform cell gap.
The normal configuration for the resist layer 13 with uniform thickness between the rigid mold 11 and the substrate 15 is shown in FIG. 1A. However, unavoidable and uncontrolled particle contamination in patterned media manufacturing leads to tenting of the rigid mold. This forms a large area defect in the finished product. The defect configuration with an undesirable rigid particle 17 between the rigid mold 11 and the rigid substrate 15 is shown in FIG. 1B. The particle causes an increase in the resist film thickness. The resist film thickness variation produces features on the substrate that result in unacceptable data errors in the patterned media disk product. These drawings respectively depict the rigid mold on the substrate with a uniform film of resist, and the rigid mold on the substrate with a hard contamination particle leading to a non-uniform resist film thickness.
Flexible molds for other types of nano-imprinting have been prepared from poly dimethyl siloxane (PDMS) such as Sylgard 184. However, PDMS-based flexible molds have limited resolution and they undergo swelling in organic solvents and resists. Flexible templates for patterned media have been made from hydrocarbons and siloxanes. These designs present difficulties in separation from the cured resist, and have significant durability issues since they do not last for many molding cycles. Thus, although conventional solutions are workable for some applications, improvements in manufacturing magnetic media would be desirable.